This invention relates to a method of disposing solid sodium chloride, more particularly it relates to a method of disposing solid sodium chloride while selectively solution mining potassium chloride from a subterranean ore deposit.
Potassium chloride is solution mined from subterranean deposits containing potassium chloride and sodium chloride by circulating through the deposit water or an aqueous solvent unsaturated with respect to potassium chloride. A solution richer in potassium chloride than the solvent is withdrawn from the deposit as a cavity is developed therein. Potassium chloride values are extracted from the enriched solution in an above ground process.
By solution mining in this manner with water as a solvent both potassium chloride and sodium chloride are extracted from the deposit non-selectively. However, as the temperature is increased and as the sodium chloride content of the solvent is increased, the more selectively the potassium chloride is mined from the deposit (i.e., the greater the ratio of KCl/NaCl mined). Hence, the composition and temperature of the solvent can be adjusted to efficaciously mine a deposit according to its ratio of potassium chloride to sodium chloride, see for example U.S. Pat. No. 3,058,729 to Dahms, et al.
These deposits typically contain high sodium chloride content i.e., sodium chloride content so high that for each kilogram of potassium chloride values produced by a refinery process such as where a solution of potassium chloride containing ore is concentrated by evaporation and subsequently cooled or where ore is treated by froth flotation, approximately two kilograms of sodium chloride are produced. Hence, on an average the ore contains about twice as much sodium chloride as potassium chloride. Unfortunately, the subterranean ore deposits are not uniform but comprise potassium chloride-rich and potassium chloride-lean strata. Therefore, where attempts are made to selectively mine upwardly through each stratum, difficulties are encountered because extraction of potassium chloride from a potassium chloride-lean stratum will not cause sodium chloride crystals to loosen; consequently, a sodium chloride barrier for further extraction is incumbent. On the other hand, where all strata are non-selectively mined, enormous quantities of sodium chloride must be discarded, either as a solid or in solution.
U.S. Pat. No. 3,366,419 to Pasternak, et al. discloses a method of non-selectively and selectively mining strata alternately lean and rich in potassium chloride by using solvents unsaturated and saturated with respect to sodium chloride, respectively. Also solid sodium chloride is slurried with solvents saturated with respect to sodium chloride during selective mining, thereby avoiding accumulation of produced sodium chloride. This method is undesirable since strata are mined upwardly therethrough whereby it is difficult to ascertain exactly when transitions between a rich and lean strata are encountered. Moreover, many rich strata are so thin that they are not detected or is not worth the emcumbrance of switching to selective mining. Further, by the time produced solution is analyzed for ore composition ratio, difficulties which are to be avoided, e.g., plugging of conduits, can arise before adjustments are made. Hence, shutdowns during the process can be experienced. Additionally, selective mining in this manner is a relatively slow process, even at relatively high temperatures. Hence, this method produces potassium chloride at an undesirably slow continuous rate.
It is therefore a desideratum that sodium chloride be disposed into a cavity in a manner that is less burdensome and conducive to fast production rates.